I find that those syntactic markers make it so much easier to parse the structure of code at a high level, and their lack (or the way they can be embedded inside other expressions) are what has always kept me away from a variety of languages, from Lisp and Forth all the way to CoffeeScript and Haskell.
In fact I think that only 13 "functions" are "magic" in clojure (as in written in java), and the whole rest of the language is written using those 13 functions[1]. That would be like, for example, adding golang's channels to ruby syntax by writing ruby code, without having to drop down to C, which i think is pretty cool.
I also found it very useful in real-life, mostly through having clojure libraries that can do things more seamlessly than similar libraries in other languages. For my last project, I needed to use maybe monad functionality quite often, and having it be as easy to use as the core language in my code was a huge win for my sanity.
[1]: I think some of the data structures are written in java as well, but only for performance reasons.